19 



The Pear=Tree Psylla (Psylla pyricola), Figs. 30, 31. Many com- 

 plaints have been made of late years respecting- injuries to Pear-trees by 

 this minute insect. It belongs to the same order as the plant-lice and 

 scale insects which are so prolific and destructive. The winter is passed 

 in crevices of the bark, or in rubbish or other shelter, by the mature 

 winged fly, which is brick-red in color and about an eighth of an inch in 

 length. About the middle of April the fly comes out of its hiding place 

 and lays its yellow eggs on buds and twigs wherever there is a crease 

 or scar to afford protection. In three weeks' time the eggs hatch and 

 the nymphs attach themselves to the leaves or opening buds. Like the 

 aphids, they secrete large quantities of "honey dew" which drips upon 

 the foliage and branches below, and becomes covered with a black fungus 

 growth. As there are several broods, probably four, in the year, the 

 colonies increase and multiply enormously, and are a heavy drain upon 

 the vitality of the tree. Fortunately they are kept somewhat in check 

 by their natural enemies the Aphis-lions (Chrysopa) and the Lady-bird 

 beetles, which in both larval and adult stages devour immense numbers 

 of them. 



a- 



/Tr'\ 



Fig. 30 — Pear-tree Psylla, greatly enlarged. 

 (After Marlatt). 



Fig. 31 — Pear-tree Psylla, a egg, b nymph, 

 greatly enlarged. (After Marlatt). 



The best remedy for the insect is a thorough application of the lime- 

 sulphur wash in early spring, as recommended for several other insects. 

 Lime alone would be effective, but the addition of sulphur helps to clean 

 off the black fungus, and the complete mixture serves at the same time 

 for the eradication of scale and other pests. If it should be found neces- 

 sary to treat the trees in summer kerosene emulsion will kill the nymphs, 

 but it is likely at the same time to kill our friends the Aphis-lions and 

 Lady-bird beetles, and may also injure the foliage. 



The Pear-Tree Slug (Selandria cerasi). Leaves of pear trees may 

 sometimes be noticed hanging withered and brown on the twigs, and 

 others with transparent patches where all ought to be green. A close in- 

 spection of the latter will usually reveal a small slimy blackish or deep 



